Electronic instruments of an aircraft at high altitudes require special measures to prevent an “arc discharge” that is occurred at high attitudes easily, since the air at high altitudes is less dense and the conducting impedance of air at high altitudes is lower than that on the ground.
The so-called “Arc Discharge” refers to an electric spark in an arc shape that occurs between two electrodes when a high-voltage power is applied between the two electrodes, and the two electrodes are drawn closer with each other to a specific distance. Electric arc (also known as corona) is similar to lightning caused by thundercloud, except that lightning fleets, and an electric arc between two electrodes lasts long to form heat accumulation. In the field of electronic circuits, arc discharge often ruins the functions of electronic components and damages electronic circuits. More seriously, arc discharge may even cause fire and jeopardize our life and safety.
In electronic instruments of an aircraft, the secondary side high-voltage output terminal of a high-voltage transformer forms an electric arc caused by an arc discharge very easily. Since a traditional transformer 1 usually has to go through an insulation process that adopts an insulating varnish 11 in a dipping process (as shown in FIG. 1A), and the temperature difference between high altitude and ground causes a brittle peeling due to the thermal expansion and contraction effect on the cured insulating varnish 11 as shown in FIG. 1B, so that a crevice 13 produced by the brittle peeling of the insulating varnish 11 is formed between an electric contact at a high-voltage terminal of the transformer 1 and the primary side input electrode terminal of the transformer 1, or an electric arc is formed by an adjacent electronic instrument. In U.S. Pat. Nos. 7,095,162 and 7,235,916, the inventor of the present invention disclosed a piezoelectric blade anchoring structure, wherein the piezoelectric blade is mounted onto a circuit board, and the piezoelectric blade has an electric contact thereon, and a conductive member is electrically connected between the electric contact and the circuit board, such that the conductive member is attached with the electric contact by a protecting plate at normal condition to prevent a gap or a loosening condition occurred between the piezoelectric blade and the conductive member due to vibrations and prevent oxidation to assure a good electrical connection effect of the piezoelectric blade and circuit board and prevent damages. However, the adhesiveness of the protecting plate applied to aircrafts at high altitude may lose its efficacy due to the thermal expansion and contraction effects, and the electric arc effect is conducted non-directionally from a low-voltage point of a device proximate to the high-voltage output terminal, so that the conductive member is only protected by the protecting plate, but it is not completely isolated. As a result, the risk and concern still exist.